Ask The Expert—Questions and Answers

Welcome to Gear Technology's Ask the Expert—a regular feature intended to help designers, specifiers, quality assurance and inspection personnel in addressing some of the more complex, troublesom gearing challenges that never cease to materialize.

Questions already answered

Questions needing answers

Aug 06, 2012 -- I am planning on using a 14.5 deg 24 pitch 20 tooth spur gear to drive a 14.5 deg 24 pitch 60 tooth spur gear. What is the maximum torque which can be applied to the 20 tooth gear? Both gears have a face width of .25".posted by Anonymous

Jul 13, 2012 -- Bevel gears used in differentials seem to be forged in most automotive applications. Old developments are Gleason Coniflex cut developments, but it seems modern developments are computer generated. I have never seen anything about who does this and wonder if this is true and why it is not in the news.posted by Jimmy Ream, QMS Inc.

Jun 19, 2012 -- What kind of data must be considered when we grind a gear with profile shift?

A few days ago we received a series of gears that need to be corrected (Profile shift), and our engineering department has a question about this topic. They told me that they do not know how to calculate the gears with profile shift. They suspect that with each profile shift factor the pressure angle also changes.

A friend in Texas told me "you cannot make a profile shift gear with a normal cutter. For each correction factor you require a cutter according to the modification." Is this correct? posted by Anonymous

May 28, 2012 -- It is very difficult to set a pair of bevel gears by trial and error in order to get the ideal backlash and contact pattern. For our regular gear technicians at sites, this involves a lot of time for assembly. Often, we have to hire outside professionals, even after paying high charges for spares.

Can there be a faster/easier method to arrive at the ideal combination?
posted by Anonymous

May 23, 2012 -- I work for VALEO since 1999 manufacturing Motor Wiper Systems and I've never found a method to inspect correctly the tip and root diameter or radius of our gear parts (pinion and wheel with spur or twisted teeth in plastic POM or worm in steel).

Most recently, we have used a caliper, but this method does not give satisfactory results (R&R > 30%). I would like to know if there are some other methods to inspect these dimensions, such as optical or LASER methods.

For your information, our modules are between 0.5 to 1.5 mm, the dimensions to inspect are between 8 to 65 mm and our tolerances for the tip or root diameter are between 50 to 350 μm.

Thanks for your answer.

Best regards,
C. LASSALLEposted by Christophe Lassalle, VALEO Wiper System

May 23, 2012 -- We are doing Pinion Gear hobbing process (Module 1.75 and Helix angle of 20degrees). During Hobbing the Helix angle Lead error maintained within 20 microns. But after Heat treatment in Sealed Quench furnace, Helix angle lead variation observed up to 70 microns.

Is there any improved process to minimize Heat treatment distortion, so that Lead values can be controlled?posted by D VARADHARAJAN, RANE TRW STEERING SYSTEMS LTD